The present invention relates to power operated doors of the type in which the doors are reversibly moved between an open and closed position by a motor driven door operator actuated by one or more selectively operable control switches. Such power operated doors may, for example, be of the type disclosed in U.S. Patents of Robert E. Slopa et al, U.S. Pat. Nos. 2,927,788 and 3,261,128. In such power operated doors, it is also common practice to provide a releasable connection between the door and the door operator, which releasable connection is operable by emergency release handles located at both the inner and outer sides of the door to disconnect the doors from the door operator and allow manual movement of the door.
Locking of such power operated doors to prevent unauthorized entry from the outside, presents some problems. It is not satisfactory to merely lock the door to the door casing as is the custom with non-powered operated doors, since the power operator would remain operable and might be damaged if someone operated the control switch for the door operator while the door operator was locked. Moreover, even when it is desirable to lock the doors against unauthorized entry from outside, it is still necessary to allow the doors to be manually moved to their open positions from the inside of the room for emergency exit.
The U.S. patent to Clark, U.S. Pat. No. 2,835,487, discloses an apparatus for locking the doors from the outside in which a hasp is swingably attached to one door and is movable into engagement with a keeper attached to another door so that the doors can be locked in a closed position by a conventional padlock. The swingable hasp is arranged to operate a switch that disables the door operator, when the hasp is in its locked position, and the keeper is mounted so that it can be detached by manipulating a member on the inside of the other door so that the keeper while still locked to the hasp, can swing with the hasp to the open position of the latter. This mechanically unlocks the doors and also reestablishes power to the door operator. The doors can then be manually moved to their open position by operating the emergency release handle to disconnect the door from the door operator. Thus, in order to make an emergency exit from the room locked by the apparatus disclosed in the Clark patent, it is necessary to operate several different instrumentalities in a particular sequence. Moreover, as soon as the door is unlocked, power is reestablished to the door operator. This presents some possibility for injury to someone making an emergency exit, if the door operator is actuated while he is attempting to manually move the door. Further, after making an emergency exit through the doors, it is necessary to remove the padlock from the keeper and hasp, reassemble the keeper on the door, and thereafter move the door to its closed position, in order to enable relocking of the door.